CN117250690B - Optical field focusing method and device for on-chip waveguide integration - Google Patents
Optical field focusing method and device for on-chip waveguide integration Download PDFInfo
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12083—Constructional arrangements
- G02B2006/12107—Grating
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12133—Functions
- G02B2006/12147—Coupler
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Abstract
The application provides an optical field focusing method and device for on-chip waveguide integration. The device comprises: the device comprises a substrate, a rectangular waveguide module, an annular waveguide module and a grating module; etching the rectangular waveguide module and the annular waveguide module on the surface of the substrate; the rectangular waveguide module is used for conducting laser and dividing the laser into multiple paths of laser; the annular waveguide module is used for receiving the multiple paths of laser and diffracting the multiple paths of laser into an annular light field; the grating module is used for responding to the annular light field, diffracting the annular light field into a diffraction light field through a circular grating array in the grating module, and finally focusing the diffraction light field. The method and the device overcome the defect that the existing light field focusing scheme is not easy to integrate on-chip in large scale. And the silicon optical production process is compatible with the existing silicon optical production process, the volume and the size are reduced, the cost is reduced, the mass production is realized, and the focal length selection range is wider.
Description
Technical Field
The application relates to the field of silicon-based optoelectronic chips, in particular to an optical field focusing method and device for on-chip waveguide integration.
Background
Light field focusing refers to converging laser beams at a point in space to generate a gradient light field, which is a light intensity distribution form of a light vector field, and the light field under the distribution form can capture tiny particles in a force mode. The scheme is not only a core technology of various optical tweezers systems, but also is widely applied to the fields of laser processing, biomedical sensing, light wave angular momentum characteristic exploration, micro-flow control and the like. However, the acquisition of the on-chip gradient light field has a great difficulty.
To obtain a near-surface gradient light field, this can be achieved generally by the following three methods:
(1) The use of high numerical aperture lenses to produce stable gradient light fields is however bulky and expensive, while the use of tapered lens optical fiber modifications is still not suitable for large scale on-die integration.
(2) The scheme can be suitable for integration on large-scale chips by means of the generation of a gradient light field by means of evanescent waves of planar photonic devices, but the attenuation length (hundreds of nanometers) of the evanescent fields is too short so that the scheme can only perform two-dimensional particle operation on the near surface of the chip.
(3) The 3D printing polymer free-form surface is used for generating a focusing light field, and the focusing light field can enable laser beams to be converged at one point in space, so that a gradient light field is generated. The optical field of the scheme has higher adjustability, but the free-form surface of the polymer cannot be compatible with the existing silicon light production process, so that the mass production is difficult.
Aiming at the problems of higher cost, shorter focusing distance and incapability of mass production in the method for generating the gradient light field or focusing the light field in the related technology, no effective solution is proposed at present.
Disclosure of Invention
Based on the foregoing, it is necessary to provide a method and apparatus for optical field focusing integrated by on-chip waveguide.
In a first aspect, the present application provides an on-chip waveguide integrated optical field focusing device. The device comprises:
the device comprises a substrate, a rectangular waveguide module, an annular waveguide module and a grating module.
Etching the rectangular waveguide module, the annular waveguide module and the grating module on the surface of the substrate;
the rectangular waveguide module is used for conducting laser and dividing the laser into multiple paths of laser; wherein the multiple paths of lasers are uniformly distributed around the annular waveguide module;
the annular waveguide module is used for receiving the multiple paths of laser and diffracting the multiple paths of laser into an annular light field;
the grating module is used for responding to the annular light field, diffracting the annular light field into a diffraction light field through a circular grating array in the grating module, and finally focusing the diffraction light field; the circular grating array is formed by 360-degree rotation of a focusing grating coupler around the center of the annular light field.
In one embodiment, the substrate has a waveguide index of refraction that is greater than the cladding index of refraction.
In one embodiment, the substrate is a material compatible with micro-nano processing, including SOI (Silicon-On-Insulator), silicon nitride, silicon oxide, III-V compounds, lithium phosphate, polymers, and the like.
In one embodiment, the rectangular waveguide module is composed of an outer rectangular waveguide unit, a conical waveguide unit and an inner rectangular waveguide unit;
the outer rectangular waveguide unit divides the laser into multiple paths of laser, and the multiple paths of laser are incident to the conical waveguide unit;
the tip end of the conical waveguide unit is connected with the outer rectangular waveguide unit, the bottom end of the conical waveguide unit is connected with the inner rectangular waveguide unit, and the conical waveguide unit is used for gradually expanding the multipath laser incident by the outer rectangular waveguide unit and transmitting the multipath laser to the inner rectangular waveguide unit;
the inner rectangular waveguide unit is connected with the annular waveguide module and is used for making the multipath laser expanded by the conical waveguide unit incident to the annular waveguide module.
In one embodiment, the laser is split into two parts by a beam splitting coupler and enters into separate outer rectangular waveguide units respectively, and the beam splitting process is repeated for a plurality of times, so that the laser is finally split into multiple paths of lasers.
In one embodiment, the annular light field is diffracted upward at a preset angle after passing through the circular grating array to become the diffracted light field, and the preset angle is determined according to the focusing grating coupler.
In one embodiment, the diffracted light field is focused in free space in the form of dark field focusing; the free space is located above the center position of the grating module.
In one embodiment, the focusing grating coupler is a chirped grating coupler, and the width of the unetched portion of the chirped grating coupler decreases from outside to inside from the center of the grating module.
In a second aspect, the present application further provides an optical field focusing method of on-chip waveguide integration, which is applied to an optical field focusing device of on-chip waveguide integration, where the device includes a substrate, a rectangular waveguide module etched on the surface of the substrate, an annular waveguide module, and a grating module; the method comprises the following steps:
the rectangular waveguide module conducts laser and divides the laser into multiple paths of laser; wherein the multiple paths of lasers are uniformly distributed around the annular waveguide module;
the annular waveguide module receives the multiple paths of laser and diffracts the multiple paths of laser into an annular light field;
the grating module responds to the annular light field, diffracts the annular light field into a diffraction light field through a circular grating array in the grating module, and finally focuses the diffraction light field; the circular grating array is formed by 360-degree rotation of a focusing grating coupler around the center of the annular light field.
In a third aspect, the present application also provides an optical tweezers system on chip, comprising a laser source, a coupling device, a detection device, and an optical field focusing device integrated with an on chip waveguide as described in the first aspect above.
Compared with the prior art, the optical field focusing method and device for on-chip waveguide integration have the following beneficial effects:
the rectangular waveguide module, the annular waveguide module and the grating module are etched on the surface of the substrate, so that the rectangular waveguide module, the annular waveguide module and the grating module are compatible with the existing silicon light production process, the volume and the size are reduced, the cost is reduced, and mass production is realized; the grating module is used for responding to the annular light field, diffracting the annular light field into a diffraction light field through a circular grating array in the grating module, and finally focusing the diffraction light field, and meanwhile, the grating module has a larger focal length selection range.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application. It is apparent that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 shows a block diagram of an optical field focusing device integrated with an on-chip waveguide in one embodiment of the present application;
FIG. 2 shows a distribution diagram of a rectangular waveguide module in one embodiment of the present application;
FIG. 3 is an enlarged view of a portion of FIG. 2 at A;
FIG. 4 shows a schematic diagram of a circular grating array in one embodiment of the present application;
FIG. 5 shows a schematic diagram of a chirped grating coupler according to one embodiment of the present application;
FIG. 6 shows a flow diagram of an optical field focusing method of on-chip waveguide integration in one embodiment of the present application;
FIG. 7 shows a block diagram of an optical tweezers system on chip in one embodiment of the present application;
FIG. 8 shows a schematic structural diagram of an optical field focusing device integrated with an on-chip waveguide in a preferred embodiment of the present application;
FIG. 9 shows a distribution of the optical field of the waveguide layer in a preferred embodiment of the present application;
FIG. 10 shows a distribution diagram of a focused light field in a preferred embodiment of the present application;
fig. 11 shows a plot of the size of a focused spot in a preferred embodiment of the present application.
Detailed Description
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, whereby the invention is not limited to the specific embodiments disclosed below. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. All other embodiments obtained without inventive effort fall within the scope of protection of the present invention.
In one embodiment, as shown in FIG. 1, there is provided an on-chip waveguide integrated optical field focusing device 100 comprising: a substrate 110, a rectangular waveguide module 120, a circular waveguide module 130, and a grating module 140, wherein:
the surface of the substrate 110 is etched with the rectangular waveguide module 120, the annular waveguide module 130 and the grating module 140;
the rectangular waveguide module 120 is configured to conduct laser light and divide the laser light into multiple paths of laser light; wherein the multiple lasers may be of different wavelengths or phases and uniformly distributed around the annular waveguide module 130;
the annular waveguide module 130 is configured to receive the multiple paths of laser beams, and diffract the multiple paths of laser beams into an annular optical field;
the grating module 140 is configured to diffract the annular light field into a diffracted light field through a circular grating array in the grating module 140 in response to the annular light field, and finally the diffracted light field is focused; the circular grating array is formed by 360-degree rotation of a focusing grating coupler around the center of the annular light field.
The rectangular waveguide module 120, the annular waveguide module 130 and the grating module 140 are etched on the surface of the substrate 110, so that the conventional silicon light production process is compatible, the volume and the size are reduced, the cost is reduced, and mass production is realized; the grating module 140 is configured to diffract the annular light field into a diffracted light field through a circular grating array in the grating module 140 in response to the annular light field, and finally, the diffracted light field is focused and has a larger focal length selection range.
In one embodiment, the waveguide index of the substrate is greater than the cladding index.
The difference in the refractive index of the substrates allows the energy of the optical signal to reach very far receiving ends with near zero loss, which is easier for large scale integration.
In one embodiment, the substrate is of a material compatible with existing micro-nano processing techniques, including, but not limited to, SOI (Silicon-On-Insulator), silicon nitride, silicon oxide, III-V compounds, lithium phosphate, polymers, and the like. For example, the substrate may be formed using a Silicon-On-Insulator (SOI) structure, consisting of a bottom Silicon layer, a middle thinner Silicon oxide layer, and a top 220nm thick thinner Silicon layer. All micro-nano structures, namely the rectangular waveguide module, the annular waveguide module and the grating module are etched on the top silicon layer.
The substrate material is compatible with the existing micro-nano processing technology, so that the scheme of the application can be integrated on a large scale.
In one embodiment, as shown in fig. 2 and 3, the rectangular waveguide module is composed of an outer rectangular waveguide unit 210, a tapered waveguide unit 220, and an inner rectangular waveguide unit 230;
the outer rectangular waveguide unit 210 divides the laser light into multiple laser light paths, which are incident to the tapered waveguide unit 220;
as shown in fig. 3, the tip of the tapered waveguide unit 220 is connected to the outer rectangular waveguide unit 210, the bottom is connected to the inner rectangular waveguide unit 230, and the tapered waveguide unit 220 is used for expanding multiple optical fields transmitted along the outer rectangular waveguide unit 210 to optical fields transmitted along the inner rectangular waveguide unit 230;
the inner rectangular waveguide unit 230 is connected to the annular waveguide module 240, and is configured to make the multiple laser beams incident on the annular waveguide module 240.
It should be noted that the dimensions of the outer rectangular waveguide unit 210, the tapered waveguide unit 220 and the inner rectangular waveguide unit 230 are not limited to the dimensional relationships shown in fig. 3, and the dimensional relationships of the units in the rectangular waveguide module in the practical device can be adjusted according to practical needs as long as the width of the outer rectangular waveguide unit 210 is smaller than the width of the inner rectangular waveguide unit 230. Meanwhile, the tapered waveguide of the process may be an adiabatic tapered waveguide to reduce energy loss during light transmission.
This process transitions the smaller mode field transmitted along the outer rectangular waveguide unit 210 to the larger mode field transmitted along the inner rectangular waveguide unit 230, enabling the optical field distributed in a near-circular shape to enter the circular waveguide module 240 along the waveguide layer.
In one embodiment, the laser is split into two parts by a beam splitting coupler and enters into separate outer rectangular waveguide units respectively, and the beam splitting process is repeated for a plurality of times, so that the laser is finally split into multiple paths of lasers.
In one embodiment, the diffracted light field is focused in free space in the form of dark field focusing; the free space is located above the center position of the grating module.
By the dark field focusing principle, when the upward diffracted annular light beams are focused, light fields in different horizontal directions are mutually overlapped and offset, the light spot size of the final focused light field is greatly reduced, and the full width at half maximum of the light spot of the focused light field is finally obtained to be 2.1um and is close to the diffraction limit.
In one embodiment, the focusing grating coupler is a chirped grating coupler, and the width of the unetched portion of the chirped grating coupler decreases from outside to inside from the center of the grating module.
As shown in fig. 4, the etching width of the circular grating array 330 increases gradually along the direction from outside to inside of the center of the grating module, that is, the width of the unetched portion of the chirped grating coupler decreases gradually;
as shown in fig. 5, the annular optical field 410 becomes a diffracted optical field 420 after passing through the chirped grating coupler 400; along the direction from the annular optical field 410 to the transmissive optical field 430, the width of the recessed portion of the chirped grating coupler 400 increases continuously, and the width of the etched portion also increases gradually, i.e., the width of the unetched portion of the chirped grating coupler decreases.
In one embodiment, as shown in fig. 5, the annular light field 410 is diffracted upward at an angle to generate a diffracted light field 420 after passing through the circular grating array, while a transmitted light field 430 and a leaky light field 440 are generated in the transmission direction and the substrate (i.e., base) direction.
The grating parameters such as etching depth, duty ratio, linear factor and the like are reasonably set, the duty ratio of the diffraction light field 420 can be adjusted, different grating coupling efficiency and diffraction angles are further obtained, and the final focusing light field is also different.
Based on the same inventive concept, as shown in fig. 6, the application also provides an optical field focusing method of on-chip waveguide integration, which is applied to an optical field focusing device of on-chip waveguide integration, wherein the device comprises a substrate, a rectangular waveguide module etched on the surface of the substrate, an annular waveguide module and a grating module;
in one embodiment, the method comprises:
step S510, the laser source generates polarization maintaining laser, and the polarization maintaining laser is incident to the rectangular waveguide module on the substrate;
step S520, the rectangular waveguide module conducts laser and divides the laser into multiple paths of laser; wherein the multiple paths of lasers are uniformly distributed around the annular waveguide module;
step S530, the annular waveguide module receives the multiple paths of laser and diffracts the multiple paths of laser into an annular light field;
step S540, the grating module diffracts the annular light field into a diffracted light field through a circular grating array in the grating module in response to the annular light field, and finally the diffracted light field is focused; the circular grating array is formed by 360-degree rotation of a focusing grating coupler around the center of the annular light field.
The optical field focusing device integrated by the on-chip waveguide can be applied to various optical tweezers systems, and can also be widely applied to the fields of laser processing, biomedical sensing, optical wave angular momentum characteristic exploration, micro-flow control and the like, which need to focus an optical field or a gradient optical field.
Based on the same inventive concept, as shown in fig. 7, the present application further provides an on-chip optical tweezers system, which comprises a laser source, a coupling device, a detection device, and the on-chip waveguide integrated optical field focusing device according to any one of the above embodiments.
In one embodiment, the laser source generates polarization maintaining laser light, and the coupling device is used for coupling the polarization maintaining laser light generated by the laser into the chip waveguide and generating a focused light field in a dark field focusing form by the light field focusing method integrated by the chip waveguide. The detection device is used for observing and measuring the position and dynamic behavior of an object operated by the optical tweezers system.
The device of the present application will be described in more detail below with reference to a schematic structure of an optical field focusing device integrated with an on-chip waveguide in the preferred embodiment of fig. 8.
The focusing device comprises an SOI substrate 610, a rectangular waveguide array 620, an annular waveguide array 630, a circular grating array 640 and a focusing light field 650; the whole optical field focusing method is that the waveguide is etched on the SOI substrate 610, the non-periodic structure diffracts and focuses the optical field of the waveguide layer to a specific position, and all micro-nano structures (the rectangular waveguide array 620, the annular waveguide array 630 and the circular grating array 640) are etched on the 220nm thick silicon layer at the top of the SOI; the rectangular waveguide array 620 is formed by uniformly dividing one rectangular waveguide into 16 rectangular waveguides surrounding the annular waveguide array 630, and each waveguide angle uniformly surrounds the outside of the annular waveguide array 630. The laser light of a specific polarization state generated by the laser source is equally divided into 16 parts to be incident into the annular waveguide array 630. The light fields transmitted by the 16 rectangular waveguides are diffused and overlapped in the annular waveguide array 630, and finally an annular light field is generated and radiated to the internal circular grating array 640; light transmitted in the circular grating array 640 will be diffracted into free space at a certain angle after passing through the sub-wavelength non-periodic structure, forming an annular focusing light field on the near-chip surface, and finally the diffracted light will be focused in the center of the space on the chip in a dark field focusing manner.
The following describes the parts of the preferred embodiment device in detail.
In a preferred embodiment, the substrate 610 contains all chips with a waveguide index of refraction greater than the cladding index of refraction, including but not limited to silicon, silicon nitride, silicon oxide, III-V compounds, lithium phosphate, polymers, and the like. In the preferred embodiment, the chip uses a Silicon-On-Insulator (SOI) Silicon-On-Insulator structure consisting of a bottom Silicon layer with a middle thinner Silicon oxide layer and a top 220nm thick thinner Silicon layer, all micro-nano structures being etched in the top Silicon layer.
In a preferred embodiment, rectangular waveguide array 620 is comprised of an outer rectangular waveguide, a tapered waveguide, and an inner rectangular waveguide. Laser generated by the semiconductor laser outputs TE polarized laser to enter the outer rectangular waveguide after passing through the polarization controller, the waveguide width is 0.5um, and the coupler 22 outputs light 1:1 is divided into two parts and enters into independent outer rectangular waveguides respectively, the last process is repeated through the distribution of the design layout, and finally 16 paths of outer rectangular waveguides which are distributed around the center at equal length and equal angles are obtained. The outer rectangular waveguide is then transitioned into the inner rectangular waveguide by the adiabatic taper waveguide, the inner rectangular waveguide having a width of 7um, the purpose of this process being to transition the smaller-sized mode field transmitted along the conventional outer rectangular waveguide to the larger mode field transmitted by the inner rectangular waveguide, so that the annular waveguide can be accessed along the waveguide layer with a near annular distributed optical field, the optical field distribution of which is referenced in fig. 9; all rectangular waveguides are etched on the silicon layer at the top of the SOI chip, and the etching depth is 220nm.
The light fields transmitted by the 16 rectangular waveguides will be diffused and overlapped in the annular waveguide array 630, ultimately producing an annular light field. Thereafter, annular waveguide array 630 transmits an annular optical field to the outer end of circular grating array 640, so far that the optical field transmitted along the waveguide layer begins to be diffracted into free space by the grating structure. In the preferred embodiment, the circular grating array 640 is formed by 360 ° rotation of the focusing grating coupler about the center of the circle. The input optical field is diffracted upwards at a certain angle to generate a diffraction optical field after passing through the grating coupler, meanwhile, a transmission optical field and a leakage optical field are generated in the transmission direction and the substrate direction, grating parameters such as etching depth, duty ratio, linear factor and the like are reasonably set, the duty ratio of the diffraction optical field can be maximized, and the maximum grating coupling efficiency is obtained.
The grating coupler used in the preferred embodiment mainly utilizes the diffraction principle of light, and diffracts the light transmitted in the micro-sized waveguide into free space through a sub-wavelength periodic or non-periodic structure at a certain angle, wherein the incident light and the diffracted light wave vector meet the Bragg condition:。
wherein k is g For incident wave vector, k 0 For the diffracted wave vector, Λ is the grating period, θ is the diffraction angle, and according to the first bragg condition, the grating period can be expressed as:。
λ c is the wavelength of incident light, n eff Is the effective refractive index of the grating:。
where F is the grating period duty cycle, n 0 、n e The effective refractive indexes of the original silicon layer and the etched silicon layer are respectively. The diffraction angle of the readily available grating of formula (3) is primarily dependent on the etch depth and duty cycle.
The chirped focusing grating structure is used, the width of the grating etching part increases gradually from the outside of the annular light field center to the inside of the annular light field center, and the duty ratio of the chirped grating is as follows:。
wherein F is the grating duty cycle, F 0 Is the initial grating duty cycle, which is typically determined by the minimum linewidth value, the preferred embodiment is 80nm; r is a linear offset factor; z is the light transmission distance. The coupling efficiency of the grating is mainly determined by the etching depth and the linear offset factor R, and in the embodiment of the application, two-dimensional parameter scanning is carried out through FDTD software, so that the optimal etching depth and R of the chirped grating are respectively 130nm and 30000, and finally, a 39-degree diffraction beam is obtained, and the coupling efficiency is 54%.
The annular beam diffracted by circular grating array 640 is focused spatially inward on the chip at a 39 ° tilt angle, and the diffracted light field is finally focused at the top 25um of the center of the circle, referring to the distribution diagram of the focused light field of fig. 10 and the size diagram of the focused light spot of fig. 11. The etching depth and R are reasonably adjusted, the focusing range can be a free space of 10um to 100um right above the circular grating array 640, and different focal lengths correspond to different coupling efficiency and gradient light field spot sizes. Oblique light beam device derived from gratingThe vector with horizontal and vertical directions is similar to the dark field focusing principle, when the inclined annular light beams are converged, light fields in different horizontal directions are mutually overlapped and offset, the light spot size of the final focused light field is greatly reduced, and the full width at half maximum of the light spot of the focused light field is finally obtained and is 2.1um, which is close to the diffraction limit. The focusing light field scheme demonstrated by the embodiment of the application successfully focuses at the position of 25um on the surface of the chip, so that the near field focusing problem of the prior art scheme is solved; the silicon-based chip based on the SOI structure can be produced at low cost by means of the existing mature semiconductor processing technology; integral bodyEnabling it to be integrated on a large scale.
It should be understood that, although the steps in the flowcharts related to the embodiments described above are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application shall be subject to the appended claims.
Claims (8)
1. An on-chip waveguide integrated optical field focusing device is characterized by comprising a substrate, a rectangular waveguide module, an annular waveguide module and a grating module;
etching the rectangular waveguide module, the annular waveguide and the grating module on the surface of the substrate;
the rectangular waveguide module is used for conducting laser and dividing the laser into multiple paths of laser; wherein the multiple paths of lasers are uniformly distributed around the annular waveguide module;
the annular waveguide module is used for receiving the multiple paths of laser and diffracting the multiple paths of laser into an annular light field;
the grating module is used for responding to the annular light field, diffracting the annular light field into a diffraction light field through a circular grating array in the grating module, and finally focusing the diffraction light field; the circular grating array is formed by 360-degree rotation of a focusing grating coupler around the center of the annular light field;
the focusing type grating coupler is a chirped grating coupler, and the width of the unetched part of the chirped grating coupler is decreased from outside to inside from the center of the grating module; the diffracted light field is focused in free space in a dark field focusing form; the free space is located above the center position of the grating module.
2. The on-chip waveguide integrated optical field focusing device according to claim 1, wherein the waveguide refractive index of the substrate is greater than the cladding refractive index.
3. The On-chip waveguide integrated optical field focusing device according to claim 2, wherein the substrate is material compatible with micro-nano machining processes, the material comprising SOI (Silicon-On-Insulator), silicon nitride, silicon oxide, III-V compounds, lithium phosphate, polymers.
4. The on-chip waveguide integrated optical field focusing device according to claim 1, wherein the rectangular waveguide module is composed of an outer rectangular waveguide unit, a tapered waveguide unit, and an inner rectangular waveguide unit;
the outer rectangular waveguide unit divides the laser into multiple paths of laser, and the multiple paths of laser are incident to the conical waveguide unit;
the tip end of the conical waveguide unit is connected with the outer rectangular waveguide unit, the bottom end of the conical waveguide unit is connected with the inner rectangular waveguide unit, and the conical waveguide unit is used for gradually expanding the multipath laser incident by the outer rectangular waveguide unit and transmitting the multipath laser to the inner rectangular waveguide unit;
the inner rectangular waveguide unit is connected with the annular waveguide module and is used for making the multipath laser expanded by the conical waveguide unit incident to the annular waveguide module.
5. The on-chip waveguide integrated optical field focusing device according to claim 4, wherein the laser light is stepwise split into multiple laser light by a spectral coupler.
6. The on-chip waveguide integrated optical field focusing device according to claim 1, wherein the annular optical field is diffracted upward at a predetermined angle after passing through the circular grating array to become the diffracted optical field, the predetermined angle being determined according to the focusing grating coupler.
7. The optical field focusing method of the on-chip waveguide integration is characterized by being applied to an optical field focusing device of the on-chip waveguide integration, wherein the device comprises a substrate, a rectangular waveguide module etched on the surface of the substrate, an annular waveguide module and a grating module; the method comprises the following steps:
the rectangular waveguide module conducts laser and divides the laser into multiple paths of laser; wherein the multiple paths of lasers are uniformly distributed around the annular waveguide module;
the annular waveguide module receives the multiple paths of laser and diffracts the multiple paths of laser into an annular light field;
the grating module responds to the annular light field, diffracts the annular light field into a diffraction light field through a circular grating array in the grating module, and finally focuses the diffraction light field; the circular grating array is formed by 360-degree rotation of a focusing grating coupler around the center of the annular light field;
the focusing type grating coupler is a chirped grating coupler, and the width of the unetched part of the chirped grating coupler is decreased from outside to inside from the center of the grating module; the diffracted light field is focused in free space in a dark field focusing form; the free space is located above the center position of the grating module.
8. An on-chip optical tweezers system comprising a laser source, a coupling device, a detection device, and an on-chip waveguide integrated optical field focusing device according to any one of claims 1 to 6.
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| US7376309B2 (en) * | 2006-02-28 | 2008-05-20 | International Business Machines Corporation | Optical structure |
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| CN103430065A (en) * | 2011-03-05 | 2013-12-04 | 阿尔卡特朗讯 | Radial optical coupler |
| CN114265146A (en) * | 2022-01-27 | 2022-04-01 | 中山大学 | Microcavity-waveguide coupling structure for realizing single photon source on chip and design method thereof |
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